Wave attenuation model for dephasing and measurement of conditional times

Jayannavar, A. M.; Benjamin, Colin

doi:10.1007/s12043-002-0131-3

Cited by 2 publications

(2 citation statements)

References 24 publications

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“…We use the standard notation where negative(positive) k values represent (counter-)clockwise propagating waves. The ring-lead coupling is modeled by assigning scattering amplitudes at the ring-leads junctions [40][41][42][43][44][45][46] as shown in Fig. 2b.…”

Section: (B) Scattering In the Continuous Ring Modelmentioning

confidence: 99%

Magnetic fields effects on the electronic conduction properties of molecular ring structures

2012

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While mesoscopic conducting loops are sensitive to external magnetic fields, as is pronouncedly exemplified by observations of the Aharonov-Bohm (AB) effect in such structures, the small radius of molecular rings implies that the field needed to observe the AB periodicity is unrealistically large. In this paper we study the effect of magnetic field on electronic transport in molecular conduction junctions involving ring molecules, aiming to identify conditions where magnetic field dependence can be realistically observed. We consider electronic conduction of molecular ring structures modeled both within the tightbinding (Hückel) model and as continuous rings. We also show that much of the qualitative behavior of conduction in these models can be rationalized in terms of a much simpler junction model based on a two-state molecular bridge. Dephasing in these models is affected by two common tools: the Büttiker probe method and coherence damping within a density matrix formulation. We show that current through benzene ring can be controlled by moderate fields provided that several conditions are satisfied: (a) conduction must be dominated by degenerate (in the free molecule) molecular electronic resonances, associated with multiple pathways as is often the case with ring molecules; (b) molecular-leads electronic coupling must be weak so as to affect relatively distinct conduction resonances; (c) molecular binding to the leads must be asymmetric (e.g., for benzene, connection in the meta or ortho, but not para, configurations) and, (d) dephasing has to be small. When these conditions are satisfied, considerable sensitivity to an imposed magnetic field normal to the molecular ring plane is found in benzene and other aromatic molecules. Interestingly, in symmetric junctions (e.g. para connected benzene) the transmission coefficient can show sensitivity to magnetic field that is not reflected in the current-voltage characteristic. The analog of this behavior is also found in the continuous ring and the two level models. 2Although sensitivity to magnetic field is suppressed by dephasing, quantitative estimates indicate that magnetic field control can be observed in suitable molecular conduction junctions.3

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Section: (B) Scattering In the Continuous Ring Modelmentioning

confidence: 99%

Magnetic fields effects on the electronic conduction properties of molecular ring structures

2012

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“…A scattering matrix approach [121,92,122,119,123,125,126] can now be used in order to give a quantitative description of the present model. Within this approach one labels each part of the wavefunction on every conducting wire with a different amplitude which designates its traveling direction.…”

Section: Two-terminal Devicesmentioning

confidence: 99%

Magnetoresistance of nanoscale molecular devices based on Aharonov–Bohm interferometry

Hod

Baer

Rabani

2008

J. Phys.: Condens. Matter

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Control of conductance in molecular junctions is of key importance in the growing field of molecular electronics. The current in these junctions is often controlled by an electric gate designed to shift conductance peaks into the low bias regime. Magnetic fields, on the other hand, have rarely been used due to the small magnetic flux captured by molecular conductors (an exception is the Kondo effect in single-molecule transistors). This is in contrast to a related field, electronic transport through mesoscopic devices, where considerable activity with magnetic fields has led to a rich description of transport. The scarcity of experimental activity is due to the belief that significant magnetic response is obtained only when the magnetic flux is of the order of the quantum flux, while attaining such a flux for molecular and nanoscale devices requires unrealistic magnetic fields. Here we review recent theoretical work regarding the essential physical requirements necessary for the construction of nanometer-scale magnetoresistance devices based on an Aharonov-Bohm molecular interferometer. We show that control of the conductance properties using small fractions of a magnetic flux can be achieved by carefully adjusting the lifetime of the conducting electrons through a pre-selected single state that is well separated from other states due to quantum confinement effects. Using a simple analytical model and more elaborate atomistic calculations we demonstrate that magnetic fields which give rise to a magnetic flux comparable to 10(-3) of the quantum flux can be used to switch a class of different molecular and nanometer rings, ranging from quantum corrals, carbon nanotubes and even a molecular ring composed of polyconjugated aromatic materials. The unique characteristics of the magnetic field as a gate is further discussed and demonstrated in two different directions. First, a three-terminal molecular router devices that can function as a parallel logic gate, processing two logic operations simultaneously, is presented. Second, the role of inelastic effects arising from electron-phonon couplings on the magnetoresistance properties is analyzed. We show that a remarkable difference between electric and magnetic gating is also revealed when inelastic effects become significant. The inelastic broadening of response curves to electric gates is replaced by a narrowing of magnetoconductance peaks, thereby enhancing the sensitivity of the device.

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Wave attenuation model for dephasing and measurement of conditional times

Cited by 2 publications

References 24 publications

Magnetic fields effects on the electronic conduction properties of molecular ring structures

Magnetic fields effects on the electronic conduction properties of molecular ring structures

Magnetoresistance of nanoscale molecular devices based on Aharonov–Bohm interferometry

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